1. Field of the Invention
The present invention relates to, for example, an image forming apparatus that charges in accordance with an amount of printing, and to a page classification method for charging in an image forming apparatus.
2. Description of the Related Art
Conventionally, as a charging approach in an image forming apparatus, charging is performed according whether the printing is color printing or monochrome printing. However, toner amount consumed based on the number of color pixels in images is different when performing different color printing. For this reason, uniform charging for color printing at a single classification may be undesirable from the viewpoint of both a service provision side and a user side. So, a technique recited in Japanese Patent Laid-Open No. 2010-89486, which counts the number of color pixels that satisfy fixed conditions for each page and which switches a charge classification based on the number of color pixels or a color pixel utilization rate, is proposed.
However, in the technique recited in Japanese Patent Laid-Open No. 2010-89486, a case where a size of the sheet that is printed is unknown is not considered. For example, in a case a free size printing, in which the size of the sheet is not specified explicitly, there are issues in that the number of color pixels recorded on a sheet is also unknown, and a calculation of a color pixel utilization rate is not performed correctly.
For example, in a case of printing when setting an A4 size sheet in an image forming apparatus, the image forming apparatus can generate output image data to match the A4 size which is the output sheet size. For this reason, a calculation of the number of color pixels or the color pixel utilization rate can be performed based on an actual region printed on a paper.
However, in a case of a free size printing, the sheet size is unknown at the time of generating output image data. Even though a main scanning direction length is detectable by a guide of a paper feeding unit, there is no way to know an actual sheet size for an image forming apparatus side, because there is no size detection means for a sub-scanning direction length and a size input by a user is not performed. For this reason, in a case of a free size printing, neither the number of color pixels nor a color pixel rate based on a sheet size can be calculated, and so a charge classification based on these values cannot be adopted.